I am replying to your crosspost into the Medical Students forums (good move because you never know)...
I can't really answer the question, but that's where talking to PD's and residents would help. Check out
Home | Mysite .
On the academic side of the house, it has been discussed, so I would expect some responses:
Considerations for Residency Programs Regarding Accepting... : Academic Medicine .
As you also surmise, getting admitted to many OMFS programs would require admission to medical schools (MD), so it would also help you if you knew
which medical schools accept DACA recipients. So I would start with OMFS programs associated with those medical schools in asking your questions.